I would say albums as an art form overall. Yes of course some bands and musicians will still write an album in this way, but music has been playlist-ified to the point where most people won't listen to it like that. You take a song or two from it and forget the rest exist. My perception is that it's been a dying thing for some time now.
I also pick off my favourite songs from most albums, to be fair. But there are some albums that are best viewed as a single piece of art and I feel like that understanding from both listeners and artists is dying. If you just listen to Money and Breathe (In the Air) when they show up in your shuffle, are you really listening to Dark Side of the Moon?